Biomedical subjects
Publications and source records attributed to S B Thompson.
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To examine the effect of risk area size on collateral resistance and ischemic region perfusion, we produced different sized risk areas by occluding either the left anterior descending (LAD) or the circumflex (Cx) coronary artery at different sites. The most proximal occlusion of the LAD and Cx produced risk areas of 43 +/- 5 and 36 +/- 2% of left ventricular (LV) mass, respectively, whereas distal LAD and Cx occlusions produced risk areas of 13 +/- 2 and 17 +/- 2% of LV weight, respectively. Although total collateral flow was highest to the largest risk areas, collateral flow per 100 g of ischemic myocardium was 80% higher to the small LAD risk area compared with the large LAD risk area and 43% higher to the small Cx risk area compared with the large Cx risk area. Collateral resistance, calculated from the transcollateral pressure and perfusion per 100 g of myocardium was significantly lower in the small risk areas than in the large ones. We examined the effect of risk area location on collateral perfusion and resistance. Small risk areas (6% LV mass) were created near the base and at the apex of 10 hearts. Collateral flow per 100 g was 60% higher and transcollateral resistance per 100 g 50% lower at the apex than at the base. These experiments show that collateral resistance is influenced both by ischemic region size and location. Small risk areas receive more collateral flow per mass of tissue than large risk areas, and apical risk areas receive greater quantities of collateral flow than those located at the base.(ABSTRACT TRUNCATED AT 250 WORDS)
A system for testing quadriceps performance is described involving a microcomputer, quadriceps switch, analogue-to-digital converter, electromyograph, and an interface unit that rapidly converts quadriceps contraction to a digital signal to be read by a microcomputer. A computer program, developed in response to a need for new patient assessment schedules in active rehabilitive therapy for strokes, tests the patient's control over function of the quadriceps muscle in the affected leg. The software is written in BBC BASIC and designed to run on an Acorn BBC Model 'B' microcomputer. Speed of interpretation of inputs is a few milliseconds.
The effect of an indwelling intravenous cannula on sleep-EEG measures has not been extensively documented despite its relatively frequent use in a variety of clinical studies. When the sleep EEGs from 30 healthy subjects were critically examined, no changes in sleep architecture were found. However, there were significant differences in the distribution of sleep latency, maintenance, and efficiency, with many subjects showing a reduction in the latter two items on the night of cannulation. A decrease in sleep maintenance of greater than 7.5 on the night of cannulation has been used to operationally define an unsatisfactory cannulation study which accounted for 43% of our subjects. It was striking that this group could also be identified by having higher REM densities in each REM period on the previous two nights in the sleep laboratory. This was especially true for the second REM period on the second night when only three of those subjects with subsequent unsatisfactory studies had a REM density less than 0.9. When this criterion was applied to a new group of 19 subjects, 13 were correctly classified with respect to subsequent changes in sleep maintenance before the cannulation study was conducted. It therefore appears possible that REM-sleep measures can be used to predict which subjects will have disrupted sleep on a subsequent cannulation night. Since sleep disruption can significantly mask patterns of hormone secretion, it is essential to monitor the sleep-EEG during such studies.
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The complaint of knee pain is frequent in children. The difficulty of obtaining an accurate history from the younger child adds to the already-difficult problem of establishing an accurate diagnosis from clinical examination and routine radiographs in this group. This report is a prospective study of 32 children less than 18 years of age who underwent arthroscopy either because their symptoms failed to resolve with conservative treatment or because knee surgery was planned. The findings suggested some important differences between these children over 13 years of age and those age 13 years or younger. In the preadolescent group, 36% gave a history of trauma, 27% were correctly diagnosed before arthroscopy, and the correct diagnosis was delayed for an average of 18 months, as compared to 20%, 61% and nine months, respectively, for the older group. Three major problem areas were identified in the preadolescent group that could be solved by arthroscopy: serious intraarticular damage from long-unrecognized internal derangements; the difficulty of diagnosing the cause of synovitis; and the syndrome of persistent pain with no demonstrable knee pathology. Arthroscopy in the preadolescent patient is a safe and useful tool in those unusual cases with persistent and undiagnosed knee symptoms.